Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$115.52	13.422%	$131.0251	$131.03	$131.05	$131.00
Purchase #2	$88.90	12.648%	$100.1441	$100.14	$100.15	$100.10
Purchase #3	$76.27	8.782%	$82.968	$82.97	$82.95	$83.00
Purchase #4	$144.88	4.850%	$151.9067	$151.91	$151.90	$151.90
Purchase #5	$147.86	4.291%	$154.2047	$154.20	$154.20	$154.20
Purchase #6	$32.69	3.626%	$33.8753	$33.88	$33.90	$33.90
Purchase #7	$101.33	12.518%	$114.0145	$114.01	$114.00	$114.00
7 purchase totals =	$707.45		$768.1384	$768.14	$768.15	$768.10